Bring up-to-parity with Fris' Light Version

[DazedNConfused-]

Resolves #49
Resolves #51

[DazedNConfused-]

PS: Also resolves #34

It doesn't do it in the way discussed in #34 (it may potentially restore incompatible-after-the-update mods), but this was the implementation @Fris0uman came up with. Keeping parity with his Light-version fork, within the realms of compatibility, is one of the tenets of this repo. Also, it solves the fundamental point that was aggravating some users, so I cannot argue with the results.

[Fris0uman]

The code I brough back in my PR #19 was never removed from this fork so I don't see how it could help here. Either there is a deeper issue or #34 is an invalid issue for this version of the launcher

[DazedNConfused-]

@Fris0uman You are right. After comparing that particular cherry-picked commit with the current build, I see that no changes are effectively applied in the mod-handling part. I am by no means a Python virtuoso, but looking at the code I see that it should be restoring the mods in the "previous" folder; tho #34 claims that isn't happening.

I don't play with mods myself, so I haven't personally tested this behaviour. I shall have to do a test of my own and see what happens when a mod is in place.